From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750768AbWGFTmJ (ORCPT ); Thu, 6 Jul 2006 15:42:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750765AbWGFTmJ (ORCPT ); Thu, 6 Jul 2006 15:42:09 -0400 Received: from main.gmane.org ([80.91.229.2]:39352 "EHLO ciao.gmane.org") by vger.kernel.org with ESMTP id S1750768AbWGFTmH (ORCPT ); Thu, 6 Jul 2006 15:42:07 -0400 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= Subject: Re: [patch] spinlocks: remove 'volatile' Date: Thu, 06 Jul 2006 20:41:54 +0100 Message-ID: References: <20060705114630.GA3134@elte.hu> <20060705101059.66a762bf.akpm@osdl.org> <20060705193551.GA13070@elte.hu> <20060705131824.52fa20ec.akpm@osdl.org> <20060705204727.GA16615@elte.hu> <20060705214502.GA27597@elte.hu> <20060706081639.GA24179@elte.hu> <1152187268.3084.29.camel@laptopd505.fenrus.org> <44AD5357.4000100@rtr.ca> <44AD658A.5070005@nortel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Complaints-To: usenet@sea.gmane.org X-Gmane-NNTP-Posting-Host: agrajag.inprovide.com User-Agent: Gnus/5.1007 (Gnus v5.10.7) XEmacs/21.4.15 (Security Through Obscurity, linux) Cancel-Lock: sha1:2MCP+PkaYhwUtrcaQpNXNhEjjCQ= Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "Chris Friesen" writes: > Linus Torvalds wrote: > >> On Thu, 6 Jul 2006, Mark Lord wrote: > >>> A volatile declaration may be used to describe an object corresponding >>> to a memory-mapped input/output port or an object accessed by an >>> aysnchronously interrupting function. Actions on objects so declared >>> shall not be "optimized out" by an implementation or reordered except >>> as permitted by the rules for evaluating expressions. >> Note that the "reordered" is totally pointless. >> The _hardware_ will re-order accesses. Which is the whole >> point. "volatile" is basically never sufficient in itself. > > The "reordered" thing really only matters on SMP machines, no? No, each CPU does write combining and write merging all on its own. -- Måns Rullgård mru@inprovide.com